I'm looking for a book that I once read where wizards were divided into different factions.
One of those factions had a foot as a banner and they provide the source (e.g. the magic) that the other wizards need to do their magical works. If done properly they calculate how much a wizard needs.
Since they can only draw on magic (but not apply the energy themselves) they have to walk whereas other wizards can float/fly. Hence their order name.
Which book am I thinking is this?
I believe this is the Darksword series by Margaret Weis and Tracy Hickman. There are 9 different categories of magic user. The ones who supplied magic to others were known as Catalysts. Catalysts could use very little magic but could supply it to others.
Most other magic users could fly (although those with weak magic might require the assistance of a Catalyst). However, Catalysts typically needed to walk since they could not accept magic from another Catalyst. Their symbol is the shoe (Thanks to FuzzyBoots for pointing this out).
Of course, our protagonist isn't. One of the cursed ones that has neither magic nor the power to fuel it. The Catalysts seem like the real victims here, by the way. Their symbol is the shoe. Because they have to WALK. Because they aren't magical like EVERYONE ELSE. But they provide juice for everyone else's magic.
